Method and apparatus utilizing detonation waves for spraying and other purposes



Aug. 2, 1955 PQORMAN ETAL 2,714,563

METHOD AND APPARATUS UTILIZING DETONATION WAVES FOR SPRAYING AND OTHERPURPOSES Filed March 7, 1952 2 Sheets-Sheet l I 17 s xjg; COIL 7 i Q;ACETYLENE' 2 ACETYLENE 28 INVENTORS RICHARD M. POORMAN YG HERBERTB.SARGENT OX EN g HEADLEE LAMPREY A'TToRNEY g- .g. i

Aug. 2, 1955 R. M. POORMAN ET AL 2,714,563

METHOD AND APPARATUS UTILIZING DETONATION WAVES FOR SPRAYING AND OTHERPURPOSES Filed March 7, 1952 2 Sheets-Sheet 2 Ed 33 WW 03 4.

32 I I SPARK COIL 2 ACETYILENE+ POWDER A A A Tl W6 (Tungsten Carbidealloy) (Steel base) INVENTORS J 5 RICHARD M. POORMAN y- HERBERT B.SARGENT r I HEADLEE LAMPREY h AT ORNEY METHOD AND APPARATUS UTILIZINGDETONA- TION WAVES FOR SPRAYING AND OTHER PURPGSES Richard M. Poorman,Speedway, and Herbert B. Sargent, Indianapolis, Ind, and HeadleeLamprey, Lakewood, Ghio, assignors to Union Carbide and CarbonCorporation, a corporation of New York Application March 7, 1952, SerialNo. 275,332

27 Ciaims. (Cl. 117105) This invention relates to new methods of usingdetonations and to novel apparatus for making, controlling, and usingdetonations.

By the term detonation is meant a very rapid combustion in which theflame front moves at velocities higher than the velocity of sound in theunburned gases, and therefore characterized as supersonic velocities.(Typical calculated velocities of sound at normal pressure are 1085 feetper second at 18 C. in a 50% oxygen-50% acetylene mixture, 1384 in thesame mixture at 200 C., and 1122 at 18 C. in a 9.5% acetylene-90.5% airmixture; in air at 18 C. the sonic velocity is calculated as 1122 feetper second.) The rate of flame propagation is far greater in adetonation than in an explosion, which is a combustion in which thevelocity of flame propagation does not exceed the velocity of sound inthe unburned gases. According to Wilhelm Josts Explosion and CombustionProcesses in Gases. McGraw-Hill Book Co., Inc., New York (1946), pages160 to 210 of which are devoted to detonations, the velocity of theflame front in detonations thus far investigated is from 1 to 4kilometers per second (about 3,280 to 13,120 feet per second), ascompared to, for instance, 50 feet per second for a typical explosion.

The flame of a detention moves into the unburned gas with a velocitywhich is supersonic instead of subsonic, and it is initiated by andremains associated with a shock front. Once established in a long tube,the detonation wave travels at a constant velocity (Lewis and Von Elbe,Combustion, Flames and Explosions, Academic Press Inc., 1951).

Detonations in gases have not been considered commercially useful. Wherethey have occurred they have been objectionable. An object of thisinvention is to utilize the phenomenon of a detonation in helpful andvaluable ways. For example, the invention uses detonations to impart ahigh velocity and a high temperature to particles, and to project thespeeding particles against a surface for coating, cleaning, breaking, orboring, and for other purposes.

In accordance with the invention, a single fluid fuel charge or a rapidsuccession of fluid fuel charges of proper composition to be detonatedare fed to a gun where they are ignited to establish a single detonationor a series of detonations following one another at short timeintervals. Into this gun, in one aspect of the invention, particles suchas powder are introduced in such manner that they are accelerated by thedetonation and its associated phenomena and projected from the open endof the gun onto a surface.

The invention will be more particularly described with reference to theaccompanying drawings, in which:

Fig. 1 is a view, partly diagrammatic, of one form of detonation gunembodying the invention;

Fig. 2 is a view of a modification of the gun shown in Fig. 1;

Fig. 3 is a view, also partly diagrammatic, of a further modification ofthe gun shown in Fig. 1;

Eatented Aug. 2, 1955 Fig. 4 is a side elevational view, also partlydiagrammatic, of still another modification of a detonation gun; and

Fig. 5 is a photomicrograph, at 300 diameters magnification, showing alayer of tungsten carbide-cobalt alloy deposited on a steel workpiece bythe method of the invention.

According to the embodiment shown in Fig. 1, a combustible gas, such asacetylene, is supplied through a pipe 10, and an oxidizing gas, such asair, is supplied through a pipe 11, to a mixing chamber 12 where theyform a detonating gaseous charge mixture which moves through a shortconnecting pipe 13 into an ignition chamber 14 provided with a sparkplug 15. Sparking of the spark plug 15 ignites the charge, leading tothe formation of a detonation wave which travels through a barrel 16 ofthe gun and out its open end. The firing of the spark plug 15 isaccomplished by a spark coil 17, battery 13, and cam operated switch 19.The frequency of firing is regulated by a variablespeed motor 20 whichdrives the cam of the switch 19.

Powder is introduced into and carried by the oxidizing gas fed throughthe pipe 11, or it may be carried by the combustible gas. The powderparticles are heated and accelerated by the detonation waves andpropelled from the open end of the gun barrel 16 at high velocities.

in the modification shown in Fig. 2, powder is fed into the air inletpipe 1., from a container 21 at a rate controlled by a valve 22. Apressure equalizing line 23 leads from the upstream side of the powderintroduction point 24 to the headspace of the powder container 21. Topromote thorough mixing of the combustible gas and the oxidant theformer is introduced into the mixing chamber 12 from two opposite sidesthrough pipes 10 and 10a. Detonation conditions are improved byproviding a small ignition chamber 140: of initially less diameter thanthat of the barrel 16, which diameter gradually increases towards thebarrel.

We have found that under some operating conditions, for instance whenusing oxygen and acetylene, it is desirable to have a positive closurebetween the ignition chamber and the gas supply. Also, under somecircumstances, for instance when using very fine powder or low meltingpowders, it is advantageous to introduce the powder downstream of theignition chamber so that the power will not deposit in the chamber.These features are indicated in Fig. 3 which shows poppet valves 25operated in conventional fashion by a motor 26 and cam 27 to obtain thedesired frequency of opening and closing of the valves. A powderintroduction pipe 28 is shown between the ignition chamber 14 and theopen end of the gun barrel 16. Coatings have also been made when thepowder was introduced between the open end of the barrel and theworkpiece.

The detonation gun shown in Fig. 4 is similar to that of Fig. 3 exceptthat an inert gas such as nitrogen is introduced into the gun from aconduit 29 through a poppet valve 31, to purge the mixing chamber andthereby protect the valves. Valve 31 is operated by a second cam 32 oncam shaft 33 which is so constructed and arranged relatively to cam 27and so correlated with a spark timing cam 34 that the following timedsequence of operations occurs:

1. Cam 27 opens poppet valves 35 and 37 simultaneously to admitcombustible gas and oxidant (with or without powder) to the gun.

2. Cam 27 then permits poppet valves 35 and 37 to close.

3. Immediately after valves 35 and 37 close, cam 32 opens poppet valve31 and admits inert nitrogen gas to the gun. Nitrogen gas flows acrossvalves 35 and 37 to dilute any leaks from such valves which might causeflashback upon detonation of the mixture.

4. Immediately after nitrogen valve 31 opens, and while it remains open,cam 34 fires the gun.

5. After detonation occurs nitrogen from open valve 31 flows through thegun to drive out the hot combustion products, and forms a protectivewall between them and the next combustible mixture charge.

' 6. Cam 32 then permits nitrogen valve 31 to close and the cycle isready to repeat with the reopening of valves 35 and 37 to form the nextcombustible mixture.

There is wide latitude of choice in the dimensions of the gun barrel 16,provided that the length is at least several times the diameter of thebore. If the barrel is too short, the gas mixture will not detonate. Atoneinch inner diameter We have successfully used lengths from fifteen toone hundred and twenty inches. Somewhat shorter barrels are much lessefiicient although usable with some gas mixtures. Our best results withone-inch inner diameter barrels have been achieved with barrel lengthsfrom three to six feet. Using /2 inch inner diameter pipe we have founda length of eight inches to be usable with some gas mixtures but threefeet to be more generally suitable.

Simple air cooling is ordinarily adequate for the gun barrel. If in aparticular use of the gun, for instance for nearly continuous use withoxygen-acetylene mixtures it is found that the barrel gets too hot, itmay be water cooled. Poorly cooled corners and edges within the ignitionand mixing chambers should of course be avoided to prevent thedevelopment of hot spots which could cause too early ignition.

The forms of apparatus shown in Figs. 1 and 2 operate without valves inthe gas lines. In these forms the oxidizing and fuel gases should besupplied at about the same pressure to reduce the danger of backfire. Aconventional backfire arrester may be inserted in the fuel supply linefor greater safety.

The detonation Wave may be generated in a wide variety of fluids andfluid mixtures. Liquid fuels such as gasoline may be vaporized and used.Solid fuels such as coal powder may be suspended as dusts in a gas tomake a fluid mixture. Suitable gaseous fuels include acetylene,hydrogen, propane, butane, pentane, and

ethylene which form detonatable mixtures with an Detonation Wave Mixturefg Approx. Velocity, ft. per sec.

Hydrogen-air 29 6, 360 Acetylene-air 9 7, 200 Propane-oxygen 29 8. 540Hydrogen-oxygen- 67 9, 250 Acetylene-oxygen. 50 9, 700

The aforementioned volumes by Jost and by Lewis and Von Elbe list thepercentage ranges of composition .to provide detonatable mixtures of airor oxygen with eight different fuels, and describe detonation velocitiesfor a variety of mixtures. With oxygen the lower limit .of acetylene is3.53.6%, and the upper limit is 9293%.

With air the lower limit of acetylene is 4.2%, and the upper limit is50%.

The temperature in the detonation wave is high, for several mixturesupwards of 2800 C. However, much of the heat is dissipated before theparticles strike a workpiece so that, inherently, little heating of theworkpiece results from application of a coating. Heat distortion of theworkpiece is thus absent when using the process of the invention. Suchheating of the workpiece as may take place can readily be overcome orcompensated by interrupting the application of coating from time to timeand permitting the workpiece to cool with or without directing a blastof coo-ling fluid such as air against it. External cooling with a liquidspray or fog can also be used, as can internal water cooling when theworkpiece is hollow. Particles of a material such as tungsten carbidecan be applied securely to a workpiece having a substantially differentcoeihcient of thermal expansion, such as steel, by cooling the workpieceas described.

The flow rates of the gases may be adjusted so that the mixture justfills the gun in the time interval between igniticns, in which case thedetonation front travels to the end of the barrel. At a lower flow ratethe detonation front travels through the part of the length of thebarrel that contains detonatable gas mixture and a shock wave arisingfrom the detonation travels the rest of the way to the end of thebarrel. A greater flow rate of gas gives a flame beyond the end of thebarrel.

Although the ignition system illustrated is an adaptation of theconventional system used for internal combustion engines, it is obviousthat other ignition means, such as an electrically heated filament orinjected hot powder particles, could be used. The illustrated system isconvenient, inexpensive, and reliable.

The frequency of the detonations is a factor in attaining effectiveoperation of this detonation gun. The most useful frequency depends onthe particular use of the gun, the design of the gun, and the characterof the detonating gas mixture. A single detonation suffices when a thindeposit on a small area is desired, for example a tungsten carbidecoating .0005 inch thick on a steel surface one inch or less indiameter. For making thicker coatings, and coating larger areas quicklyseveral detonations per second are usually desirable. For instance, fc-rprojecting tungsten carbide-cobalt alloy powto form coatings on varioustools and articles with a one-inch diameter gun barrel about five feetlong using an oxygen-acetylene detonating mixture, a frequency in theneighborhood of 4 per second is very satisfactory and a frequency of 7.8has been used. For projecting aluminum powder in a similar gun using anair-acetylene detonating mixture, a frequency of 40 per second is verysatisfactory and frequencies as high as 70 have been used. Atfrequencies above 7.8 for the oxygen-acetylene mixture and 70 for theair-acetylene mixture the gun tends to overheat, and flashbacks andcontinuous burning tend to occur. With better design, the maximumfrequency theoretically would be limited only by the mechanics of valveoperation or by the rate at which gas could be flowed into the gunbetween detonations. High rates of gas flow may require inconvenient ordangerous gas pressures, and high rates of operation of the gun mayoverheat it or some parts of it.

Powders fed into the gun are accelerated to very high velocities.Particles are believed to be accelerated within the gun by one or moreof: (a) the shock front at the head of the detonation wave, (b) therapidly moving gases behind the shock front, and (c) the previouslydescribed shock wave beyond (downstream of) the detonated gas mixture.

Powder flow rates into the gun are not particularly critical except asthey influence the economics of coating formation, i. e., the cost andrapidity at which a given coating is built up. Ten pounds per hour seemsto be most advantageous for good quality of coating with maximumhardness when using 180 cubic feet per hour each of acetylene, oxygen,and nitrogen (for conveying powder and for blanketing the poppet valves)in a oneinch inside diameter gun with a detonation frequency of 4.3 persecond. Rates as low as 0.6 pound per hour, and as high as 24 pounds perhour have been used successfully with tungsten carbide powder finer than44 microns.

One practical application of the invention is to clean or roughensurfaces. For instance a rusty steel plate was effectively cleaned withsteel blasting grit of .42 to .59 millimeter particle size. Steel shotcan similarly be directed forcibly against a metal body to peen itssurface.

Another application is to pulverize frangible material. For example,diatomaceous earth powders of l to micron particle size were passedthrough the gun, thereby being reduced to 0.1 to 1 micron in size.

Another application of the detonation gun is to the spheroidizing ofpowders. When unspheroidized powder particles are shot through anoxy-acetylene detonation gun the original sharp corners and edges aremelted and rounded over, and in many cases a shape approaching sphericalis obtained. Finer particles tend to become more nearly spherical thanlarger ones, and metals become more spherical than non-metals. Metalswhich have been successfully spheroidized are chromium, Cr-Ni-B alloy,tungsten, and molybdenum. Non-metals are alumina, boron carbide, siliconcarbide, tungsten carbide, silicon nitride, chromium carbide, tungstencarbide-cobalt alloy, titanium carbide, and borosilicate glass. Particlesizes of the powder ranged up to microns in diameter. The composition ofthe gas mixture detonated in the gun was approximately .5 oxygen, 45.5%acetylene, and 9% nitrogen (the vehicle for carrying powder into thegun). The spheroidized particles may be collected in a liquid or in awax target.

The invention is particularly well adapted for coating surfaces with anyof a wide variety of metals, alloys, metallic compounds, plastics,ceramics, and minerals. Foundation surfaces may be of metal, glass,wood, cloth, paper, plastic, or other. The surface to be coated may belocated any convenient small distance from the open end of the gun, sayone-half inch to ten inches. For example, an object to be coated withtungsten carbide particles is usually spaced about three inches from themuzzle of the gun.

Good coatings on smooth glass have been made with the gun of theinvention, rising aluminum, copper, brass, tin, lead, zinc, andmagnesium powders. Copper and zinc have been applied successfully toaluminum; aluminum and nickel to carbon; aluminum to mesh stainlesssteel wire screen; aluminum and zinc to cotton cloth; aluminum to paper;aluminum, copper, magnesium, nickel, and tin to wood; aluminum tomethacrylate plastic;

tin, aluminum, molybdenum, copper, tungsten, tungsten carbide alloy,austenitic stainless steel, chromium, cobaltchromium-tungsten alloy,nickel-molybdenum alloy, boron carbide, and porcelain frit to steel; andtungsten carbide alloy to firebrick. Mixtures of various powders alsomay be deposited on a workpiece by the detonation gun. For instance afriction plate may be formed by mixing a soft metal powder such asaluminum with a powdered hard material such as alumina, passing themixture through the gun and depositing the mixture on a steel base asalumina particles in an aluminum matrix. A mixture of iron, chromium,and nickel powders may be deposited on steel to impart resistance tocorrosion and wear. It may sometimes be advantageous to include anon-metallic powdered flux with the powder to improve adhesion.

Optimum powder size is believed to be that which permits the surfaces ofthe particles to be softened enough to give good adherence but does notpermit excessive vaporization of the particles. Generally, materials oflower melting point, such as tin, lead, zinc, aluminum, and magnesiummay be of larger particle size, say up to microns, and those of highermelting point, such as chromium, tungsten, and tungsten carbide, havebeen most successfully used when smaller than about 50 microns toproduce dense adherent coatings. However, these size limits are notcritical, for instance 12 to 32 microns copper powder has been used verysuccessfully to coat aluminum, and tungsten carbide-cobalt alloy powderas coarse as 74 microns has been successfully coated on a metal body.

With aluminum powder smaller than 44 microns, a work surface about twoinches from the open end of the one-inch diameter gun, and repeateddetonations of air and 10% acetylene at a frequency of about 30 cyclesper second, a coating 0.017 inch thick by 1% inch diameter was formed ina minute and a half on a clean steel surface. This coating wassubstantially impermeable.

Copper or other readily soldered metal may be sprayed onto materialssuch as glass, porcelain, wood, plastics, or aluminum, which areunsolderable or solderable with difliculty, and the so-coated materialsthen easily soldered to form a joint.

Pieces of canvas cloth were successfully coated with aluminum and withzinc on both sides by directing the metal particles from the detonationgun against one side only of the cloth. Paper tape was also coated withaluminum while moving the tape slowly in front of the gun muzzle toavoid charring. In both cases the fuel was an air-acetylene mixture.

The method and apparatus of this invention may be used to clean or coatobjects submerged in water or other liquid, or protected by a specialatmosphere such as argon. The gun operates well under water.

A particularly interesting example of the performance capabilities ofthis invention is its use to deposit adherent coating of high-meltingpoint abrasion-resistant hard coatings such as tungsten carbidecompositions.

Finely powdered (mostly 10 to 40 microns particle size) cast tungstencarbide composition containing, apart from the tungsten, about 9% cobaltand 4% carbon is fed at a rate of about 10 to 15 pounds per hour to agun of the form shown in Fig. 4 about five feet long and one-inch insidediameter. Acetylene and oxygen are fed in a ratio of about 1 cubic footof the former to 1 to 2 cubic feet of the latter at an average rate ofabout 360 cubic feet per hour of the mixture. The average flow ofnitrogen is about cubic feet per hour total. The ignition frequency isabout four per second. A clean iron or steel surface, either soft orhard (for instance tool steel) preferably roughened as by grit blastingor thinly coated with a soft metal such as copper, nickel, or cobalt,suitably in a coating 0.00025 to 0.0005 inch thick, is p0sitioned aboutthree inches from the open end of the gun. A dense, adherent layer oftungsten carbide composition 0.02 inch thick is deposited at a rate ofabout one square inch per minute. Thinner or much thicker coatings maybe applied by varying the time of application.

Fig. 5 shows at a magnification of 300X the appearance of a tungstencarbide-cobalt alloy coating WC deposited by the process of theinvention on a steel base S. The

tungsten carbide included 9% of cobalt. The sample was polished and thengiven an anodic etch with chromic acid, followed by a potassiumpermanganate stain.

The detonation gun deposits of tungsten carbide composition are finegrained dense, lamellar structures composed of mixed layers of tungstencarbide (WC), complex carbides of cobalt and tungsten, and small amountsof a secondary tungsten carbide (W2C). These particles which form thecoating are elongated and flattened by the heat and impact imparted bythe gun into thin overlapping discs or leaves such that their diameteris many times larger than their thickness. This structure is in directcontrast to sintered carbides which have a fine dense equiaxialstructure, and tungsten carbide alloy coatings sprayed on with aconventional flame spray gun which have a relatively coarse, porous,weakly bonded structure. The conventional flame spraying method producesa coating of tungsten carbide which is formed of particles that areessentially unchanged in shape and poorly bonded while the detonationgun flattens out the particles and produces an excellent bond betweenthe individual particles.

The coating has bulk density substantially identical with that of thesolid cast material applied, 14.5 g./cc. Porosity is less than 1%.Adherence of the coating to the base is excellent, as shown by the factthat portions may be ground down to and through the interface withoutpeeling. The hardness on the Vickers scale is at least 1100. The coatinghas a smooth matte surface which may be brought to a high polish bystandard precision grinding and polishing procedures.

The properties of this coating adapt it for surfaces of such articles ascore rods used for pressing and coining, burnishing broaches, snap andplug gages, crusher jaws, shaft seal rings and plates, electricalcontacts, boring bars, saw teeth, knife blades, textile thread guides,valve seats and plugs, and bearing surfaces. For some electricalcontacts, it may be desirable to incorporate in the powder a metal ofhigh conductivity, such as silver.

This application is in part a continuation of application Serial No.19,268 and application Serial No. 239,748, both now abandoned.

What is claimed is:

1. A detonation gun comprising a barrel, a mixing chamber communicatingwith said barrel, means for separately supplying charges of an oxidizinggas and gaseous fuel to said chamber and barrel, an ignition chamberpositioned between the barrel and the mixing chamber directly andcontinuously communicating with said barrel and said mixing chamber,means for entraining powder particles in one of the components of thegaseous mixture formed in the mixing chamber, and means for detonatingcharges of the mixture repeatedly many times a second, the gun barrelbeing long enough to allow formation of a detonation wave theerin,whereby a high velocity is imparted to the powder particles.

2. A detonation gun provided with an elongated barrel, a gas mixingchamber at one end of the barrel directly and continuously communicatingwith said barrel, gas conduits provided with valves for separatelysupplying an oxidizing gas and a gaseous fuel to said mixing chamber andthence to said barrel, means for supplying powder particles to saidbarrel, an ignition chamber in the gun having an opening to the barrelof said gun, ignition means in said ignition chamber, the length anddiameter of the gun barrel being adapted for the formation andmaintenance therein of detonations, whereby powder supplied to said gunis ejected from the barrel under the impetus of said detonations.

3. A detonation gun comprising a barrel of diameter and length to permitthe formation in a fluid fuel charge of a detonation; first valve meansfor supplying successive fluid fuel charges to said barrel; second valvemeans adjacent said first valve means for supplying an inert gaspositioned to flow across said first valve means into said barrel toprotect said first valve means; and ignition means for initiating adetonation in said fluid fuel charge in said barrel.

4. A detonation gun in accordance with claim 3, also comprisingautomatic timing sequence control mechanism operatively associated withsaid first and second valve means and said ignition means, and actingfirst to open and then close said first valve means to fill said gunwith fluid fuel, then to open said second valve means to start theadmission of inert gas to said gun, then to operate said ignition meansto initiate a detonation, and after a time delay for such inert gas topurge the gaseous products of combustion from the gun acting to closesaid second valve means.

5. A method for utilizing detonation waves which comprises providing, inan elongated barrel having an open end, a detonatable body of adetonatable gas and a comminuted solid material unconsumable by thedetonation phenomena in said body, and igniting said detonatable body ofgas to produce a detonation and thereby to eject said comminutedmaterial at high velocity from the open end of said barrel.

6. A method in accordance with claim 5, wherein said detonatable gascomprises oxygen and a fuel gas selected from the group consisting ofacetylene, hydrogen, propane, butane, pentane, and ethylene. 7

7. A method for utilizing detonation waves which comprises mixing a fuelgas and an oxidizing gas to form a mixture capable of being detonated,introducing a detonatable body of said mixture into an elongated barrelhaving an open end, introducing a comminuted solid material unconsumableby the detonation phenomena in said detonatable body of said mixture,and igniting said detonatable mixture to produce a detonation andthereby transmit to said comminuted material some of the energy from atleast one of said detonation and its associated phenomena to eject saidcomminuted material from the open end of said barrel.

8. A method for utilizing detonation waves which comprises mixing a fuelgas and an oxidizing gas to form a mixture capable of being detonated,introducing a comminuted solid material unconsumable by the detonationphenomena in said detonatable mixture, introducing said detonatablemixture containing said comminuted solid material into an elongatedbarrel having an open end, and igniting said detonatable body of saidmixture to produce a detonation and thereby transmit to said comminutedmaterial some of the energy from at least one of said detonation and itsassociated phenomena to eject said comminuted material from the open endof said barrel.

9. A method for utilizing detonation waves which comprises mixing a fuelgas containing a comminuted solid material unconsumable by thedetonation phenomena with an oxidizing gas to form a mixture capable ofbeing detonated, introducing a detonatable body of said detonatablemixture containing said comminuted material into an elongated barrelhaving an open end, igniting said detonatable body of said mixture toproduce a detonation and thereby transmit to said comminuted materialsome of the energy of said detonation to eject said comminuted materialfrom the open end of said barrel.

10. A method for utilizing detonation waves which comprises introducinga comminuted solid material unconsumable by the detonation phenomenainto an oxidizing gas, mixing said oxidizing gas containing saidcomminuted material with a fuel gas to form a mixture capable of beingdetonated, introducing a detonatable body of said detonatable mixturecontaining said comminuted material into an elongated barrel having anopen end, igniting said detonatable body of said mixture to produce adetonation and thereby transmit to said comminuted material some of theenergy of said detonation to eject said comminuted material from theopen end of said barrel.

11. A method for coating an object which comprises providing, in anelongated barrel having an open end, a detonatable body of a mixture offuel gas and oxidizing gas capable of being detonated and a comminutedsolid material unconsumable by the detonation phenonema; igniting saiddetonatable body of detonatable mixture to produce a detonation andthereby transmit to said comminuted material some of the energy of saiddetonation to eject said comminuted material at high velocity from theopen end of said barrel; directing said comminuted material toward saidobject to be coated by virtue of said energy and thereafter repeatingsaid providing, igniting and directing steps at short intervals of time.

12. A method in accordance with claim ll, wherein said comminuted solidmaterial comprises a tungsten carbide composition comminuted to finerthan about 50 microns, said fuel gas is acetylene, and said oxidizinggas is oxygen.

13. A method in accordance with claim 11 wherein said mixture of fuelgas and oxidizing gas is an acetyleneair mixture containing between 7%and 13 by volume of acetylene.

14. A method for coating an object which comprises mixing a fuel gas andan oxidizing gas to form a mixture capable of being detonated, feeding acomminuted solid material unconsumable by the detonation phenomena intosaid detonatable mixture, introducing said detonatable mixturecontaining said comminuted solid material into an elongated barrelhaving an open end until said barrel is substantially filled therewith,igniting said detonatable mixture to produce a detonation and therebytransmit to said comminuted material some of the energy of saiddetonation to eject said comminuted material at high velocity from theopen end of said barrel; directing said comminuted material toward saidobject to be coated by virtue of said energy; and thereafter repeatingsaid mixing, feeding, introducing, igniting and directing steps at shortintervals of time less than one second.

15. A method in accordance with claim 11 which also comprises passing abody of an inert gas through said barrel between said providing andsubsequent ignition steps.

16. A method for coating an object which comprises mixing a fuel gas andan oxidizing gas to form a mixture capable of being detonated,introducing said detonatable mixture into an elongated barrel having anopen end until said barrel is substantially filled therewith, feeding acomminuted solid material unconsumable by the detonation phenomena intosaid detonatable mixture, igniting said detonatable mixture to produce adetonation and thereby transmit to said comminuted material some of theenergy of said detonation to eject said comminuted material at highvelocity from the open end of said barrel, directing said comminutedmaterial toward said object to be coated under the impetus of saidenergy and thereafter repeating said mixing, introducing, feeding,igniting and directing steps at short intervals of time less than onesecond.

17. A method in accordance with claim 16 which also comprises passing aninert gas through said barrel between said ignition and said subsequentintroducing steps.

18. A method for coating an object which comprises mixing a fuel gaswith an oxidizing gas to form a mixture capable of being detonated;prior to such mixing feeding into at least one of the fuel gas andoxidizing gas a comminuted solid material unconsumable by the detonationphenonema; introducing said detonatable mixture containing saidcomminuted material into an elongated barrel having an open end untilsaid barrel is substantially filled therewith; igniting said detonatablemixture to produce a detonation and thereby transmit to said comminutedmaterial some of the energy of said detonation to eject said comminutedmaterial at high velocity from the open end of said barrel; directingsaid comminuted material toward said object to be coated under theimpetus of said energy; and thereafter repeating said feeding, mixing,introducing, igniting and directing steps at short intervals of timeless than one second.

19. A method in accordance with claim 18, which also comprises passingan inert gas through said barrel between said ignition and saidsubsequent introducing steps.

20. A method of preparing for soldering surfaces of objects which arediflicult to solder directly, which comprises applying a readilysolderable metal onto the surfaces to be soldered in accordance with themethod of claim 11, thereby providing a thin adherent coating ofsolderable metal on such surfaces.

21. A detonation gun comprising an elongated barrel having an open end,said barrel having a length-to-diameter ratio sufliciently high topermit the formation of a detonation therein; mixing chamber meansdirectly and continuously communicating with said barrel for forming andpassing to said barrel charges of detonatable fluid fuel mixture; meansfor supplying the components of said detonatable fluid fuel mixture tosaid mixing chamber means; supply means associated with said barrel forproviding comminuted solid material in said detonatable fluid fuelmixture; and means associated with said barrel for igniting said fluidfuel mixture in said barrel to initiate 1 3 said detonation and propelsaid comminuted solid material from said gun.

22. A detonation gun comprising an elongated barrel having an open end,said barrel having a length'to-diameter ratio sufiiciently high topermit the formation of detonations therein; means associated with saidbarrel for providing successive quantities of a detonatable fluid fuelmixture in said barrel at regular intervals; supply means associatedwith said barrel for providing comminuted solid material in eachsuccessive quantity of detonatable fluid fuel mixture; and meansdirectly and continuously communicating with said barre] for igniting,at timed intervals, each of said successive quantities of fluid fuelmixture in said barrel to initiate a series of detonations and propelsaid comminuted solid material from said gun.

23. A detonation gun employing detonations comprising an elongatedbarrel open at one end and having an ignition chamber directly andcontinuously communicating with the end thereof, said barrel having alength-todiameter ratio sutficiently high to permit the formation of adetonation therein; means associated with said chamher for providing adetonatable fluid fuel mixture in said barrel and ignition chamber;supply means associated with said chamber for providing a comminutedsolid material in said detonatable fluid fuel mixture; and means,associated with said ignition chamber, for igniting said fluid fuelcharge in said chamber and barrel to initiate said detonation and propelsaid comminuted solid material from said gun.

24. A detonation gun employing detonations comprising an elongatedbarrel open at one end and having an ignition chamber directly andcontinuously communicating with the end thereof, said barrel having alength-todiameter ratio sufficiently high to permit the formation ofdetonation therein; means associated with said chamber for providingsuccessive quantities of a detonatable fluid fuel mixture in saidchamber and barrel at intervals; supply means associated with saidchamber for providing comminuted solid material in each successivequantity of fluid fuel mixture; and means associated with said ignitionchamber for igniting, at automatically timed intervals, each of saidsuccessive quantities of fluid fuel mixture in said chamber and barrelto initiate a series of detonations and propel said comminuted solidmaterial from said gun.

25. A method of cleaning or roughening surfaces of a workpiece utilizingdetonations and their associated phenomena which comprises providing, inan elongated barrel having an open end, a detonatable body of adetonatable gas containing a comminuted solid material unconsumable bythe detonation phenomena in said body; igniting said detonatable body ofgas to produce a detonation and its associated phenomena and therebyeject said comminuted solid material at high velocity from the open endof said barrel; and directing said comminuted solid material toward saidworkpiece surface to roughen or clean said surface.

26. A method of pulverizin g frangible material utilizing detonationsand their associated phenomena which comprises providing, in anelongated barrel having an open end, a detonatable body of detonatablegas containing a frangible solid material unconsumable by the detonationphenomena in said body; igniting said detonatable body of gas to producea detonation and its associated phenomena and thereby pulverize saidfrangible material and eject it from the open end of said barrel; andcollecting said pulverized frangible material after ejection from saidbarrel.

27. A method of spheroidizing material utilizing detonations and theirassociated phenomena which comprises providing, in an elongated barrelhaving an open end, a detonatable body of a detonatable gas containing afusible, comminuted solid material unconsumable by the detonationphenomena in said body; igniting said detonatable body of gas to producea detonation and its asso- 2,714,563 1 l 1 2 ciated phenomena andthereby fuse said comminuted solid FOREIGN PATENTS material and eject itat high velocity from said open end G t B f 1943 of said barrel, wherebysaid material is spheroidized; and Tea n am n o collecting saidspheroidized material after ejection from OTHER REFERENCES ThirdSymposium on Combustion and Flame and Exsaid barrel. 5

plosion Phenomenon, Williams & Wilkins, Baltimore, Maryland 1949, pgs.185-190.

Jost Explosion and Combustion Processes In Gas, 1946,

References Cited in the file of this patent UNITED STATES PATENTS1,375,653 McLain et al. Apr. 19, 1921 10 1,620,994 Berstamante Mar. 15,1927 2,374,816 Hansen May 1, 1945

18. A METHOD FOR COATING AN OBJECT WHICH COMPRISES MIXING A FUEL GASWITH AN OXIDIZING GAS TO FORM A MIXTURE CAPABLE OF BEING DETONATED;PRIOR TO SUCH MIXING FEEDING INTO AT LEAST ONE OF THE FUEL GAS ANDOXIDIZING GAS A COMMINUTED SOLID MATERIAL UNCONSUMABLE BY THE DETONATIONPHENONEMA; INTRODUCING SAID DETONATABLE MIXTURE CONTAINING SAIDCOMMINUTED MATERIAL INTO AN ELONGATED BARREL HAVING AN OPEN END UNTILSAID BARREL IS SUBSTANTIALLY FILLED THEREWITH; IGNITING SAID DETONATABLEMIXTURE TO PRODUCE A DETONATION AND THEREBY TRANSMIT TO SAID COMMINUTEDMATERIAL SOME OF THE ENERGY OF SAID DETONATION TO EJECT SAID COMMINUTEDMATERIAL AT HIGH VELOCITY FROM THE OPEN END OF SAID BARREL; DIRECTINGSAID COMMINUTED MATERIAL TOWARD SAID OBJECT TO BE COATED UNDER THEIMPETUS OF SAID ENERGY; AND THEREAFTER REPEATING SAID FEEDING, MIXING,INTRODUCING, IGNITING AND DIRECTING STEPS AT SHORT INTERVALS OF TIMELESS THAN ONE SECOND.